Transactions of the INDIAN CERAMIC SOCIETY Vol. 51 1992
Effects of Zn2+ Doping on the Sol-Gel Transition and Optical
Properties of Gels in Alkoxide-derived Silica
AMITAVA PATRA ASD DmYENDUGANGUU
Pages : 105-109
DOI : 10.1080/0371750X.1992.10804552
Abstract
Doped silica sols were prepared via hydrolysis and poly-condensation
reactions Involving SI(OC2H5)4 and water In which 0.5-10
mol% equivalent of ZnO was added through Zn(N03h,6H20.
Gelation wa-; found to be progressively accelerated with increasIng
amount of Zn2• which was suggested to link the silicate
polymeric clusters via terminal SiO- groups. Activation energies
of the overall process of gelation (calculated from gelling times
at 10°,30° 40° and 50°C) showed slgnlncantdrop with increasing
dopant content.
Optical absorption edges of the gel-; obtained after heating at
500° and 700°C showed progres.-;lve shifts toward-; longer wavelengths
with Increasing Zn2•; the optical band gap recorded a
corresponding decrease, suggesting this to be an effect of formation
of non-bridging Si-0-Zn groups. Another kind of
non-bridging group, namely Si-0 H, wai found by infrared spectroscopy
to decrease In amount with increase In the temperature
of heating.
